Heat Release Rate (HRR)
Calculate the heat release rate of a fire (HRR), Q̇ = ṁ × ΔH_c, multiplying the fuel burning rate (kg/s) by the effective heat of combustion (MJ/kg). The result, in MW, is the fire's power — the single most important quantity in fire science, governing gas temperatures, flame height, smoke production and spread rate. It is the fundamental input to fire safety engineering models and to the design of smoke control and detection systems. Enter the burning rate and the heat of combustion.
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Taxa de liberação de calor (HRR)
Se existe uma única grandeza que define um incêndio, é a taxa de liberação de calor (HRR, de heat release rate) — a potência do fogo. Ela é o produto da taxa de queima do combustível ṁ (massa consumida por segundo, kg/s) pelo calor efetivo de combustão ΔH_c (energia liberada por kg, MJ/kg): Q̇ = ṁ × ΔH_c, em MW. A HRR governa praticamente tudo no desenvolvimento de um incêndio: a temperatura dos gases na camada quente, a altura das chamas, a vazão da pluma de fumaça, a radiação emitida (e, portanto, a propagação para outros objetos), o momento do flashover (a ignição súbita generalizada de um compartimento) e a velocidade de crescimento do incêndio. Por isso a HRR é a entrada central de toda a engenharia de segurança contra incêndio baseada em desempenho: a partir dela, modelos de zona e de campo (CFD) calculam temperaturas, visibilidade e tenabilidade, dimensionam sistemas de controle de fumaça, posicionam detectores e verificam se o tempo disponível para escape supera o necessário. Incêndios reais costumam ser descritos por uma curva HRR×tempo (frequentemente o modelo 't²', em que a potência cresce com o quadrado do tempo). Um cesto de lixo libera ~5 kW; um sofá, 1–3 MW; um carro, ~5 MW. Informe a taxa de queima e o calor de combustão.
Related Tools
Smoke Plume Mass Flow
Calculate the mass flow of a fire's smoke plume by the Heskestad correlation, ṁ = 0.071·Q̇_c^(1/3)·z^(5/3), from the convective part of the heat release rate Q̇_c (kW) and the height above the fire base z (m). The result, in kg/s, is the amount of hot gases and smoke rising and accumulating, governing the design of smoke control and exhaust systems (mechanical or natural) that keep a smoke-free layer for safe evacuation. The flow grows strongly with height. Enter the convective heat fraction and the height.
Bearing Power Loss
Calculate the power dissipated by friction in a bearing, P = T × ω, multiplying the friction torque T by the angular velocity ω (rad/s). The result, in watts, is the mechanical energy converted to heat per unit time by friction — a loss that reduces efficiency and heats the lubricant and components. This heat must be dissipated (by convection or oil circulation) to keep a safe operating temperature, since overheating degrades the lubricant and can cause seizure. Estimating the dissipated power is essential to size the cooling and the oil flow. Enter the friction torque and the angular velocity.
Stack Heat Loss (Siegert)
Calculate the heat loss through the exhaust gases by the Siegert formula, loss = K × (T_gas − T_air) ÷ CO₂, from the fuel factor K (~0.5 for natural gas, ~0.6 for oil), the gas and combustion air temperatures (°C) and the CO₂ percentage in the gases. The result, in %, is the largest energy loss of a boiler or furnace — the heat escaping hot through the stack. Lowering the gas temperature (with economizers and preheaters) and adjusting the excess air (which dilutes CO₂) minimizes this loss. The combustion efficiency is approximately 100% minus this loss. Enter the K factor, the temperatures and the CO₂.
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